Hitherto researchers have proposed various ESD protection devices for protecting electronic devices from electrostatic discharge, or ESD.
For example, Patent Document 1 discloses an ESD protection device having an insulating substrate and first and second discharge electrodes arranged therein. The ESD protection device disclosed in Patent Document 1 has a cavity in the insulating substrate. In this cavity the first and second discharge electrodes are exposed and the ends thereof face each other. The first discharge electrode extends out of either end face of the insulating substrate. An outer electrode is on each of the pair of end faces of the insulating substrate. This ESD protection device also has a mixing portion in the area where the first and second discharge electrodes face each other, and the mixing portion is on the lower surface side of the first and second discharge electrodes and reaches the first and second discharge electrodes. The discharge aid portion contains metal particles and ceramic particles, and the metal particles and the ceramic particles are dispersed in an insulating material in the insulating substrate.
In the ESD protection device according to Patent Document 1, the shrinkage of the ceramic material contained in the insulating substrate and the first and second discharge electrodes on firing and the difference in the coefficient of the thermal expansion between these materials after the shrinkage are reduced due to the presence of the mixing portion. This ensures high precision in discharge start voltage, according to the publication.